This invention relates to LED light assemblies for the exterior of vehicles, and more particularly to such assemblies that also incorporate an electrical heater for melting snow and ice that may form on the external lens of such an assembly in cold weather.
LED lamp assemblies for use on the exterior of motor vehicles are well known in the art, as exemplified by U.S. Pat. No. 5,765,940 issued Jun. 16, 1998 to Levy et al. They have distinct advantages over the more commonly used incandescent bulbs. They have much longer useful lives, so there is less danger of unknowingly driving without the safety features the lamp is designed to provide. They are also more efficient, because a much greater portion of the electrical energy they consume is converted to useful light of the desired color. By contrast, the incandescent bulb they replace generates white light. A filtering lens absorbs the colors not desired converting it to heat, and passes only the red or yellow light required. And much of the energy is converted directly to heat. Very little of the electrical energy applied to an LED is converted to heat. While this is a distinct advantage of the LED in most situations, it poses a serious problem in cold climates. When ice or snow accumulates on the lens of the lamp housing, the incandescent lamp generates enough heat to melt the snow and ice so that it falls off and clears the lens. However, the LED assembly does not produce enough heat to do this. It is too much effort for a driver to manually clear the lamps. Consequently, these LED lamp assemblies have not been accepted in the colder climates. It would be useful to provide LED lamp assemblies that would apply enough heat to the lens to clear it of snow and ice as needed.
It is accordingly an object of the invention to provide an LED lamp assembly for the exterior of a motor vehicle that would generate enough heat to clear the lens of ice and snow. It is another object that such an assembly provide no heating when it is not needed so as to conserve energy and reduce stress on the LED""s. The heating means of the invention is connected to the electric power source through a switch that closes only when the temperature is low enough for ice and snow to accumulate on the lens. The heating means may take various forms. It may be a resistor, an infra red emitter, a resistance element embedded in the lens, or a resistance film on the lens, for example.
These and other objects, features, and advantages of the invention will become more apparent when the detailed description is studied in conjunction with the drawings in which like elements are designated by like reference characters in the various drawing figures.